Add 3D content to an image using blender
If you were using a video, you could use blender camera tracking, and add objects to the scene that way. Then, you could select the exact frame in the video that you wanted to add the objects to. For example, if you had a video of the soccer game, then you could use that.

Here is an tutorial on blender camera tracking:
https://www.google.com/url?sa=t&amp;rct=j&amp;q=&amp;esrc=s&amp;source=web&amp;cd=3&amp;cad=rja&amp;uact=8&amp;ved=0CDIQtwIwAg&amp;url=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DCVPcT0dJmoY&amp;ei=J4IoVOy7CIi9ggTB7YDwCA&amp;usg=AFQjCNF6HngfToZ3LNcfFsj9NnkfFfc6hg&amp;sig2=JLK58U_NvMz6XS_KS3IzCA